(1) Field of the Invention
The present invention relates to a coating material shrinkable at room or normal temperature (hereinafter called the room temperature shrinkable coating material or simply the coating material). More specifically, this invention pertains to a coating material of the aforesaid type which is designed to be tightly coated over the surface portions of objects such as metallic articles, for example, the joints of metal piping and the connections of electric wiring or the grip of tools etc., and has a variety of effects such as, for instance, rustproofness, weather resistance, rodent resistance, dustproofness, stickiness, antistatic properties, adhesiveness, tinting, aging resistance, etc.
(2) Description of the Prior Art
Adhesive or insulating tapes have been applied over the joints of metal pipings or the connections of electrical wirings for the rustproofing, surface protecting (against externally mechanical damage) and insulating purposes; however, their appearance upon application as well as their durability and processability have been found to be inferior or unattractive. For that reason, heat shrinkable tubing has recently been proposed and put to practical use as an alternative. Such tubing is a tubular moldings formed of, e.g., high-molecular or polymeric materials such as polyethylene or polypropylene. The moldings are forcedly stretched under a temperature condition under which they deform thermally (hereinafter referred to as the thermal deformation temperature), cooled in a stretched state, and applied over the junctions of metal articles. Subsequently, the moldings are again heated to the thermal deformaion temperature with the use of heated air, steam or a flame to allow them to shrink, thereby being restored to their original shape prior to forced stretching, whereby they are tightly coated over the said junctions in conformity with the shape thereof.
Compared with the conventional taping, this coating method has several advantages in that the coated surface is smooth, no segregation of the coating takes place due to aging of adhesives, the finished appearance is attractive, the coating excels in durability, etc. Thus, this method is applied to a wide range from the connections and joints of electric wiring and metal piping to the covers of grip portions of tools.
However, this method is disadvantageous in that it cannot be applied in a place where the use of a heating flame is prohibited, strictly due to the necessity of reheating sources for affording the thermal deformation temperature. In addition, this method involves difficulty in affording the thermal deformation temperature to the connections of internal wiring in sophisticated devices such as electronic devices, since peripheral parts are adversely affected.
In view of such considerations, room temperature shrinkable tubing has been developed which dispense with any heating for affording the thermal deformation temperature, and are now superseding the heat shrinkable tubings.
The room temperature shinkable tubing is a tubular molding formed of elastic high-molecular or polymeric materials such as, polyvinyl chloride, silicone rubber, etc. The tubular moldings are immersed in ketones, esters, liquid hydrocarbons or other volatile swelling agents, and the thus swelled moldings are stored in sealed containers. When in use, the containers are unsealed to remove the swelled moldings from inside. The moldings are then applied over the surfaces of metals to be coated, for example, the connections of electric wirings, the joints of metal pipings or the grip parts of tools, and are allowed to stand at room temperature in order that the swelling agents may be volatized. Thereupon, the tubular moldings shrink in conformity with the shape of the articles to be coated, such as metal articles, as in the case of heat shrinkable tubing, whereby they are tightly coated thereover. The present coating system is advantageous in that any heating step is dispensed with. Further, it can be applied to the surfaces of thick and sectional metal articles, such as flange joints of metal piping, to which the heat shrinkable tubing can only be applied with difficulty. To this end, polymeric moldings bearing resemblance in shape to the surfaces they are applied to are prepared, immersed in volatile swelling agents and stored in sealed containers. As occasion arises, they are removed from the containers and applied over the subject surfaces.
With all shrinkable tubing system inclusive of the heating shrinkable coating system, the subject metal surfaces are hidden from sight. Hence, any visual detection of changes, e.g., corrosive changes, in the coated metal surfaces is unlikely, except where the coating breaks accidentally due to external forces. Conversely, entrainment of moisture of other rusting matters may take place depending upon the coating manner applied, with the result that there remains a potential for rusting. It is thus preferable that rust preventives or rust resisting paints be applied; however, this would lead to extra increases in the working steps involved and thus to the corresponding disadvantages.